Analog to digital converters (ADCs) convert an analog input signal to a digital output signal. ADCs are typically implemented on an integrated circuit (IC) or chip. The output of the ADCs typically contain nonlinearity errors that need to be characterized. The nonlinearity errors may occur when the ADC has a higher gain than expected during design, a lower gain than expected during design, multiple input voltages having the same output code, and/or in other situations.
In one conventional approach for characterizing the nonlinearity of the ADC, a tone is applied to an input of ADC. Tones are sinusoidal signals having a fixed frequency. Referring now to FIG. 1, a test signal generator 10 outputs the tone to an input of an ADC 14. An output of the ADC 14 is input to a nonlinearity detector 18. The nonlinearity detector 18 is typically an off-chip device that uses conventional algorithms that detect nonlinearities in the output of the ADC 14. Time consuming post-processing must be performed to characterize the nonlinearity of the ADC 14. The post-processing is repeated for different operating conditions such as but not limited to temperature, which increases the characterization time. In some circumstances, it may take on the order of days to properly characterize the ADC 14.